WASHINGTON (RNS) Republican presidential contender Rick Santorum, leading the GOP field in national polls, is defending his views questioning prenatal testing and President Obama's "theology."

The unapologetic advocacy by Santorum seemed sure to please social conservatives in the Republican Party but also fuel questions about whether he could appeal to independent voters in a general election.

Appearing on CBS' "Face the Nation" on Sunday (Feb. 19), Santorum objected to including some prenatal tests in federal insurance mandates, saying the tests lead to more abortions.

"A lot of prenatal tests are done to identify deformities in utero, and the customary procedure is to encourage abortions," he said. "We know that 90 percent of Down syndrome children in America are aborted."

At a campaign event over the weekend in Columbus, Ohio, he said the tests effectively "cull the ranks of the disabled in our society."

He objected to provisions in the health care law that require coverage of prenatal testing for expectant mothers, saying some tests shouldn't be included. He mentioned amniocentesis, a test that can detect chromosomal abnormalities in fetuses such as Down syndrome.

The former Pennsylvania senator said he was not questioning the president's faith when, at another event in Columbus, Ohio, he said Obama's agenda followed "some phony ideal, some phony theology -- oh, not a theology based on the Bible, a different theology."

Santorum said he was referring to "radical environmentalists" who believe "that man is here to serve the Earth as opposed to husband its resources and be good stewards of the Earth."

"I wasn't suggesting the president's not a Christian," he said.

On ABC's "This Week," Obama adviser Robert Gibbs called Santorum's original remarks "over the line" and said, "It's time to have a debate on our political positions, but not question each other's character and faith."